1. Field of the Invention
This invention relates to disc saw felling heads of the type that are used in tree feller bunchers, and in particular to a construction for managing the path of chips which are cut from the kerf.
2. Discussion of the Prior Art
Feller bunchers are well known and are used for harvesting standing trees. In one type, a disc having peripheral teeth is rotated about a generally vertical axis and is advanced through the tree so that the teeth cut a horizontal kerf in the tree trunk. The teeth have radially outward tips which actually do the cutting of the kerf. When the tips are advanced all the way through the tree, the cut tree is rested on a butt plate which overlies the disc, radially inward of the teeth. The butt plate is supported by the housing of the felling head, which encloses the teeth in the zone behind the cutting and accumulating pocket. The teeth are exposed at the front of the cutting and accumulating pocket, which is necessary so as to cut the tree, and the pocket is circumscribed on its sides and rear by pocket walls. The pocket walls extend generally vertically and help restrain the tree trunks as several cut trees are accumulated on top of the butt plate in the pocket. Several trees are typically accumulated in the pocket before they are laid down to be transported or "skidded" to the roadside for loading onto a truck.
The cutting discs are relatively large in diameter (e.g. four feet) and are rotated at relatively high speed (e.g. 1,200 rpm). Thus, considerable energy is stored in the spinning disc, enough to fell a large tree in a matter of seconds. Since the height of the kerf is relatively high, on the order of about an inch or more, the volume of chips removed from the kerf is relatively high. Also, with all the energy stored by the disc, the chips are thrown a considerable distance. If rocks, dirt or other foreign objects get into the tooth path, they can be thrown even further.
As mentioned above, the teeth are only exposed outside of the housing for a limited angle of the head, at the front of the pocket. At the downstream side of the pocket (downstream meaning in the direction of rotation of the disc) there is a housing entry opening in the housing where the teeth re-enter the housing. It is a problem when so many chips or other objects are ingested through this opening into the housing so that the housing clogs, which wastes energy by slowing down the disc and causes wear to the disc, teeth and housing.
FIGS. 1 and 2 show front and top views, respectively, of a typical disc saw feller buncher head having a pocket P, a disc D, teeth T spaced about the periphery of the disc, a butt plate B forming part of the housing H, and pocket walls W. Arms A are hydraulically operated to hold cut trees over the butt plate B. The head is secured to the front of a tractor or similar vehicle (e.g., a track vehicle) and operated by the operator of the tractor to selectively fell and bunch trees as described above.
FIGS. 3-6 illustrate aspects of chip management in various prior art felling head constructions. In FIG. 3, a window O is cut in the housing H just downstream of where the teeth enter the housing H. The window O is meant to provide a space for throwing the chips out of the housing H after they enter it. Such windows are prone to becoming clogged if the volume or size of chips exceeds its capacity, especially in wet conditions. Also, chips exiting the window O can be thrown relatively large distances to the side of and in back of the head.
FIG. 4 illustrates a prior art construction somewhat similar to that shown in FIG. 3, but in which the window O is covered by a deflection plate E, which chips are intended to bounce off of and be directed downwardly. While this solves the problem of throwing the chips to the side and in back of the head, this construction is particularly prone to becoming clogged, as chips are not only restricted by the window O, but can become wedged in the duct formed between the window O and the plate E.
FIGS. 5 and 6 illustrate two different prior art heads, particularly in the area of the housing entry opening of the head. Either of these constructions may be used with the window O, or window O with deflection plate E constructions of FIGS. 3 and 4. FIGS. 5 and 6 illustrate the openings X, which are formed in the downstream pocket walls at the mouth of the pocket. While it is desirable to keep the entry opening X as small as possible, in prior art head constructions chips were still thrown or pushed into the opening X to an extent that clogging was a problem, or to an extent which made chip discharge windows or other discharge devices necessary to be cut into or added to the housing.